Synthesis and Reactivity of New Cyclomanganated (η⁶-Arene)tricarbonylchromium Complexes

Abstract

(η6-Arene)tricarbonylchromium complexes derived from N,N-dimethylbenzylamine or from benzyl methyl thioether undergo a cyclomanganation reaction when treated with PhCH2−Mn(CO)5 in boiling heptane. The manganation process is selective and involves solely aromatic C−H bond activation that yields bimetallic and trimetallic compounds, respectively, when compounds such as [(η6-C6H5CH2R)Cr(CO)3] (R = N(CH3)2, SCH3) and the diamine [{η6-C6H4-1,3-[CH2N(CH3)2]}Cr(CO)3] are reacted. Cases of transmetalation reactions consisting of the transfer of a Mn(CO)4 moiety from one aromatic ligand to another are observed with free aromatic ligands and with chromium π-complexed ligands. Two examples of bimetallic and trimetallic compounds, [(2-η)-Mn{[η6-3,5-(CH3O)2-C6H2-CH2N(CH5)2]Cr(CO)3}(CO)4] (2) and [(4-η:6-η)-{Mn(CO)4}2{{η6-C6H2-1,3[CH2N(CH3)2]2}Cr(CO)3}] (6a), respectively, were characterized by X-ray diffraction analysis. Both complexes bear distorted Mn(CO)4 units with the ancillary amino ligand pointing away from the chromium.

The Stereospecific Ligand Exchange at a Pseudo‐Benzylic T‐4 Iridium Centre in Planar‐Chiral Cycloiridium (η6‐Arene)tricarbonylchromium Complexes

“…In this respect, arenetricarbonylchromium complexes have shown excellent capabilities to undergo stereospecific metalations by mechanisms assimilated into concerted C À H bond activation. [25][26][27] It has long been known [28] that the Cr(CO) 3 moiety within (h 6 -arene)tricarbonylchromium complexes operates a characteristic stereoelectronic control over all the reactions that occur at the benzylic and pseudo-benzylic position, which promotes among other possible processes the formation of stabilised benzylic cations (Scheme 2). [29][30][31][32][33][34][35] The framework of the neighbouring group participation [36] mechanism fits reasonably well with the nucleophilic substitution reactions that involve this class of "stabilised" cations.…”

The Effect of the Trimethylsilyl Group on Electrophilic Cyclopalladation; A Study of Caryl–Si versus Caryl–H Selective Bond Activation with 2,6-(Me2NCH2)2C6H3R (R=H or SiMe3)

“…Note that directly related 1,3-biscyclomanganated complexes can be formed if the aromatic group is h 6 -bonded to a Cr(CO) 3 fragment. [17] The bis-ortho-chelated complex 8 and the bispalladium(ii) complexes 9 and 10 are not, under the conditions of our study, susceptible to further palladations of the remaining C ± H (in 8 and 9) or C ± Si bonds (10). This implies that in these species the CH 2 NMe 2 groups are effectively coordinated to the Pd II centers and that a free amine unit may be an important prerequisite for a further palladation reaction to occur.…”

The Exchange of Cyclometalated Ligands

“…The exchange in cyclometalated manganese(I) carbonyl complexes (Scheme 41), suggesting an electrophilic nature of this manganese exchange. The mechanistic options discussed included an oxidative addition to form a hydrido-Mn III complex, a multicentered process and a radical-mediated pathway [100]. Similar migrations of the Mn(CO) 4 were also reported [101,102].…”